Mapping of fluid venting and attenuation of hydrate bearing sediments from offshore Oregon
Bibliographic record
Abstract
In this article we present regional high-resolution multichannel seismic reflections surveys of the accretionary sedimentary prism off the coast of Oregon where there are strong gas hydrate-associated bottom simulating reflectors (BSRs), and indications of gas and fluid venting from the seafloor. The new data from RR1718 survey conducted in 2017 as part of a chief scientist training cruise complement previous large airgun deeper-penetration reflection surveys and International Ocean Discovery Program (IODP) seafloor drilling, which were mainly in the area of the mid-slope anticline, Hydrate Ridge. The BSRs are at depths of 120–310 ms (102–264 m) below the seafloor with the regional depths controlled by the landward decreasing heat flow, and shallower water depths. In some areas there are double BSRs interpreted to result from the thermal perturbation and sea level depth changes from transient uplift. Below the BSR there is frequent local brightening of the sediment stratigraphy reflectors by free gas. There are indications of fluid and methane gas venting from the seafloor that locally perturb the local thermal regime and the resulting BSR depth, and of seafloor carbonate caps. The lateral variation in amplitudes of the seafloor and BSR has been mapped in spectral decomposed iso-frequency sections. Attenuation estimates for the BSRs using peak frequency analysis indicate quality factors (inverse of attenuation) as low as 17 for a BSR below the anticline of Hydrate Ridge. The high attenuation is interpreted to be a consequence of a thick free gas layer.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".